Process of dyeing oranges



chromic.

United States Patent Ofiice 3,040,141 Patented July 24, 1962 Thisinvention relates to the coloration of oranges. This application is acontinuation of copending application, Serial No. 492,059, filed March4, 1955, which is a continuation-in-part of application, Serial Number415,- 420, filed March 10, 1954, now abandoned.

:For many years it has been customary to color oranges for enhancedvarietal orange to red shades. For this purpose there has been used acertified dyestuif RD. and C. Red 32 which is a mixture of cmonoazo dyesderived from a mixture of ortho, meta, and para xylidines containing themeta isomer in amounts up to 30%. The mixed xylidines are diazotized andcoupled to betanaphthol. The formerly used color, which will be referredto more briefly herein as Red 32, has a serious disadvantage in that itis by no means harmless. While its toxicity is not high, it issubstantial when large amounts of the dyestuif are administered. 'Infact, it has been decertified as a food color by the Food and drugAdministration of the U8. Government Federal Register, November 16,1955, pages 8493-8495. By present standards Red 32 is too toxic to beacceptable for coloring oranges.

This invention relates to an improved process of coloring the outer peeland depends on the use of a dyestuit of the formula:

OOH

named 1-(2,5-dimethoxyphenylazo)-2-naphthol.

The dyestuif used in the present invention is characterized bysunfastness, by extraordinarily low toxicity, far lower than that of Red32, and has shown excellent afiinity for the outer peel of oranges,which present dye ing problems.

The dyestuif used in the present invention is characterized by itssuperior tinctorial strength and by its bathochromicity. It excels thedyes of the prior art used for the dyeing of oranges, in thesequalities. The visible spectrum curve of the dyestufi used in thepresent invention demonstrates its bathochromicity in contrast to thevisible spectrum curve of Red 32 which is more hypso- The curve of thedyestuff used in the present invention shows a shift away from the curveof Red 32 toward the longer wave lengths which are characteristic ofbluer shades. This change toward longer wave length is in the directionof fuller, more natural varietal shades for oranges.

Cit is an advantage that the lack of toxicity of the dyestufi used inthe present invention is not offset by any difiiculty in applying it tothe coloring of oranges. The normal procedures used with Red 32 may beemployed and it is not necessary for the user to learn new techniques ofapplication. Thus, the dyestuif used in the present invention is appliedto the outer skin or peel of oranges (as disclosed in US. Patents No.2,068,081 to Sharma and No. 2,324,407 to Longfield-Smith with respect toRed 32) by dipping the fruit in a dye bath comprising a colloidalsuspension or solution of the dye in an aqueous medium sometimescontaining a wetting or dispersing agent and/or a solvent for thewater-insoluble dye; by spraying such a bath on the fruit; or in anyother suitable manner, such as by incorporating the dye compound in awaxy carrier applied to the oranges by rubbing and polishing.

The invention will be described in greater detail in conjunction withthe following example, the parts being by weight unless otherwisespecified.

1-(2,5-dimethoxyphenylazo)-2-naphtho1 having the formula:

in 50 parts by volume of a mixture of a substantially water-immisciblesolvent containing 25 parts by volume of a liquid hydrocarbon solvent ofBF. range l90260 C. containing about aromatic hydrocarbons, and 25 partsby volume of terpineol and adding this solution to 590 parts by volumeof 5.5% sodium oleate solution at 38 C. To 500 parts by volume of Wateris added 10 parts by volume of the dye solution and the resultantdispersion bath warmed to 50 C. The dispersion bath thus comprises anoil-in-Water emulsion, wherein the dye solution forms the oil phase.

A Valencia. orange dyed in this bath has a substantially uniform,non-removable varietal color.

Toxicity comparisons The toxicity of the dyestufl used in the presentinvention was determined and compared with that of Red 32 by acute andchronic toxicity tests on albino mice. In each test 10 mice were usedand in the chronic tests a control sample of 10 mice were given the samefood without dyestuffs. Because of the small size of the test animal,acute toxicity tests involving intraperitoneal injection present apossibility of accidental injury to an occasional mouse, thus theexperimental error of such tests is approximately 10%, or 1 mouse in asample of 10.

Acute toxicity Was determined by intraperitoneal injection at twolevels, 1024 and 2048 ing/kg. The following table shows the results interms of the number of deaths per 10 animals:

It will be noted that within the experimental error the dyestuff of thisinvention showed no acute toxicity even at the higher level. Red 32showed a very high toxicity at the higher level, mortality.

Chronic toxicity was shown by feeding tests of albino mice for 14 dayswith various concentrations-of dyestufi. As a chronic toxicity test,even for 14 days, may not give a complete picture by taking mousemortality alone, the average gain or loss in weight should be consideredbecause if there is a drastic loss in weight, this can indicate toxicityeven though some of the mice have not yet died. The first test was madewith feeding rates of 0.5 and 1.0% of dyestufi in the food. The resultsare shown in the following table:

Rate of Deaths (body wt.

It will be noticed that in the case of the first dyestufi there was nomortality at either feeding rate. With Red 32 at the lower rate, 90% ofthe mice were dead and the average loss of weight was 25%, indicatingthat even the surviving mouse was a very sick, if not actually amoribund animal. At the higher rate, mortality was 100%. Since there wasno mortality even at the higher rate with the first dyestufi, furthertests were made by feeding two other series of albino mice with a dietto which 2% and 5% of the first dyestufi was added. At the end of 28days there was no mortality even among the mice that received 5% of thedyestufi in the diet.

I claim:

1. In the process of coloring the outer peel of oranges, the improvementwhich comprises applying externally to an orange a dyestuff having theformula:

OCH;

2. The process of claim 1, wherein the dyestuff is dispersed in anaqueous medium and wherein the resulting dispersion is applied to theorange.

3. The process of claim 1, including the steps of preparing a solutionof the dyestulf in a substantially waterimmiscible solvent for said dye,dispersing a minor proportion of said dye solution in an aqueous medium,and thereafter contacting oranges with said aqueous dispersion to colorthe outer peel thereof.

4. The process of claim 1, wherein an oil-in-water emulsion is appliedto said orange, the oil phase of said emulsion being constituted of saiddyestufi dissolved in a substantially water-immiscible solvent.

5. The process of claim 4, wherein said solvent comprises a mixture ofan aromatic hydrocarbon and terpineol.

References Cited in the file of this patent UNITED STATES PATENTS2,068,081 Sharma Jan. 19, 1937 2,133,404 Shanna Oct. '18, 1938 2,224,904Elley et a1 Dec. 17, 1940 2,324,407 'Longfield-Smith July 13, 1943 OTHERREFERENCES Uses and Applications of Chemicals and Related Materials, byGregory, Reinhold Publishing Corporation, 330 West FortySecond Street,New York, N.Y., pages 589-590.

1. IN THE PROCESS OF COLORING THE OUTER PEEL OF ORANGES, THE IMPROVEMENTWHICH COMPRISES APPLYING EXTERNALLY TO AN ORANGE A DYESTUFF HAVING THEFORMULA: